Add realm names to the 2D map/exports; make diplomacy arcs a separate toggle

Kingdom/empire capital labels only ever drew on the 3D globe -- neither the
on-screen 2D map nor exportMapImage()/exportAtlasImage() showed them.
drawMapOverlays() now has a 2D realm-label block mirroring the existing 3D
one; exportAtlasImage() adds nation names as label candidates in its
decluttered pass (offset above the capital's own settlement-name anchor so
the two don't collide), shown regardless of the current colour mode since
the atlas is a reference, not "what you're looking at".

Also split the Territory view's political borders from its alliance/rivalry
diplomacy arcs, which previously always showed together with no way to hide
just the arcs. New independent showDiplomacy toggle (key A, default on, a
toolbar checkbox in Overlays) gates only the ally/rival arc draw calls.

Verified end to end: exported both Map and Atlas images from a live world
with several realms and confirmed realm names render correctly (cleanly
decluttered in the Atlas, alongside geography and settlement names).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TMfyZv91tonDnPJqbaTVJE

BUILD.md

@@ -57,7 +57,8 @@ the full ~2.8x speedup; the default uses all cores for no extra gain:
     E           ecoregions colour view (names ecological provinces on first use; Eco tab)
     I           habitability heat map (where civilization can thrive)
     U           settlements: the dawn of civilization on first press, then toggle markers (Civ tab)
-    P           territory / realms view + borders + war fronts + alliance/rivalry arcs (Realms tab)
+    P           territory / realms view + borders + war fronts + realm-name labels (Realms tab)
+    A           toggle alliance/rivalry diplomacy arcs on the Territory view (on by default)
     X           culture / faiths view + cultural borders (peoples/ethos/religion in the Cultures tab)
     Z           wealth / trade view + trade routes (sea/river/overland; prosperity feeds city growth)
     Y           follow-cam: cycle the 3D camera through active storms (Live World; off after last)

CLAUDE.md

@@ -406,6 +406,22 @@ on the Live World clock). **Steps 1–7 of the roadmap are done (plus a derived
   etc., now zero-arg methods on `Viewer`, e.g. `mode == ColorMode::Territory`) instead of stored,
   independently-mutable state — the two can no longer drift apart because there's only one source of
   truth. `src/render` only, no save-format or `src/sim` change; ctest unaffected (`src/sim` untouched).
+- **Realm names in the 2D map/exports + a diplomacy-arc toggle independent of Territory** *(done)* —
+  two follow-up requests after the above fix. (1) Kingdom/empire capital labels ("Kingdom of X") were
+  3D-globe-only (`renderFrame()`'s "3D realm labels" block); neither the on-screen 2D map nor
+  `exportMapImage()`/`exportAtlasImage()` ever drew them. `drawMapOverlays()` now has a matching 2D
+  block (same `showNationBorders() && drawLabels` gating, `projLonLat` instead of the 3D camera
+  projection; city-states skipped same as the 3D version) — fixes the on-screen map and
+  `exportMapImage()` in one place. `exportAtlasImage()` separately adds nation names as label
+  candidates in its decluttered pass (priority tier alongside cities; skipped for city-states), offset
+  above the capital's own settlement-name anchor so the two don't fight over one box; shown regardless
+  of the current colour mode, consistent with the atlas being a reference rather than "what you're
+  looking at". (2) `showNationBorders()` (Territory view) used to unconditionally show the political
+  borders **and** the Step-6 alliance/rivalry arcs together — no way to see realm borders without the
+  diplomacy lines. Added an independent `showDiplomacy` bool (default on, key **`A`**, a toolbar
+  "Alliances" checkbox in Overlays), `&&`-ed into just the ally/rival arc draw calls (3D + 2D) so
+  political borders/war fronts still show under Territory regardless — Territory now toggles cleanly
+  with or without the arcs. `src/render` only, no save-format change.
 
 ## Current state
 
@@ -930,7 +946,9 @@ all in 3D + 2D) · `N` day/night terminator (Live World) · `T` tide-coloured co
 `V` volcano markers (Live World) · `M` place-name labels (the atlas; names the world on first use) ·
 `E` ecoregions colour view (names ecology on first use) · `I` habitability heat map ·
 `U` settlements (the dawn of civilization on first press; toggles markers after) ·
-`P` territory / realms view + political borders (Realms tab lists nations) ·
+`P` territory / realms view + political borders + realm-name labels (Realms tab lists nations) ·
+`A` toggle the alliance/rivalry diplomacy arcs on the Territory view (on by default; political
+borders/war fronts stay regardless) ·
 `X` culture / faiths view + cultural borders (Cultures tab lists peoples, ethos & religion) ·
 `Z` wealth / trade view + trade routes (sea/river/overland; prosperity feeds city growth) ·
 `SPACE` or on-screen button pause ·

src/render/Toolbar.cpp

@@ -130,12 +130,13 @@ void drawToolbar(Viewer& v) {
             {"Grid (G)", &v.showGrat},         {"Rivers (J)", &v.showRivers},
             {"Day/night (N)", &v.dayNightOn},  {"Tides (T)", &v.showTides},
             {"Currents (O)", &v.showCurrents}, {"Clouds (K)", &v.showClouds},
-            {"Volcanoes (V)", &v.showVolcanoes},
+            {"Volcanoes (V)", &v.showVolcanoes}, {"Alliances (A)", &v.showDiplomacy},
         };
+        const int overlayCount = 10;
         float halfW = (cw - GAP) * 0.5f;
-        for (int i = 0; i < 9; i += 2) {
+        for (int i = 0; i < overlayCount; i += 2) {
             guiCheckRow(Rectangle{ cx, cy, halfW, ROWH }, overlays[i].label, overlays[i].flag);
-            if (i + 1 < 9) guiCheckRow(Rectangle{ cx + halfW + GAP, cy, halfW, ROWH }, overlays[i + 1].label, overlays[i + 1].flag);
+            if (i + 1 < overlayCount) guiCheckRow(Rectangle{ cx + halfW + GAP, cy, halfW, ROWH }, overlays[i + 1].label, overlays[i + 1].flag);
             cy += ROWH + GAP;
         }
         {

src/render/Viewer.hpp

@@ -110,6 +110,8 @@ struct Viewer {
     std::vector<Vector3> cultureBorders; // cultural-region border segments (civ Step 4, rebuilt with territory)
     std::vector<Vector3> warFrontier;    // red frontier segments between realms currently at war (civ Step 5)
     std::vector<Vector3> allyLinks, rivalLinks;  // civ Step 6: capital-to-capital arcs (allies green, rivals red)
+    bool showDiplomacy = true;      // draw the alliance/rivalry arcs above with the Territory view (key A) --
+                                     // independent of showNationBorders() so Territory can be shown without them
     std::vector<Vector3> tradeSea, tradeLand;    // civ Step 7: trade routes (sea cyan / river+land amber)
     long lastTerritoryYear = -1;    // sim year territory was last recomputed (recompute when it ticks)
     // Whether to draw the political/cultural/trade overlays is *derived* from `mode` -- deliberately

src/render/ViewerInput.cpp

@@ -197,6 +197,7 @@ void Viewer::handleInput() {
     if (IsKeyPressed(KEY_D))     showDrift   = !showDrift;
     if (IsKeyPressed(KEY_G))     showGrat    = !showGrat;
     if (IsKeyPressed(KEY_J))     showRivers  = !showRivers;
+    if (IsKeyPressed(KEY_A))     showDiplomacy = !showDiplomacy; // alliance/rivalry arcs with the Territory view
     if (IsKeyPressed(KEY_H)) toggleHydrology();
     if (IsKeyPressed(KEY_L)) generateOrRegenerateBiota();
     if (IsKeyPressed(KEY_E)) toggleEcoregionView();

src/render/ViewerRender.cpp

@@ -108,7 +108,7 @@ void Viewer::renderGlobe3D() {
         }
         rlEnd(); rlSetLineWidth(1.0f);
     }
-    if (showNationBorders()) {                                // civ Step 6: diplomacy arcs (allies green, rivals dark red)
+    if (showNationBorders() && showDiplomacy) {               // civ Step 6: diplomacy arcs (allies green, rivals dark red)
         rlSetLineWidth(2.0f); rlBegin(RL_LINES);
         rlColor4ub(70, 220, 120, 200);
         for (size_t i = 0; i + 1 < allyLinks.size(); i += 2) {
@@ -394,8 +394,8 @@ void Viewer::drawMapOverlays(Rectangle vr, double lonOffset, float scale, float
     if (showNationBorders() && !nationBorders.empty()) drawSegments2D(nationBorders, Color{18, 18, 26, 235}, 2.0f * scale, vr, lonOffset);
     if (showCultureBorders() && !cultureBorders.empty()) drawSegments2D(cultureBorders, Color{245, 240, 220, 230}, 2.5f * scale, vr, lonOffset);
     if (showNationBorders() && !warFrontier.empty()) drawSegments2D(warFrontier, Color{235, 40, 30, 255}, 2.5f * scale, vr, lonOffset);
-    if (showNationBorders() && !allyLinks.empty())  drawSegments2D(allyLinks, Color{70, 220, 120, 220}, 1.5f * scale, vr, lonOffset);
+    if (showNationBorders() && showDiplomacy && !allyLinks.empty())  drawSegments2D(allyLinks, Color{70, 220, 120, 220}, 1.5f * scale, vr, lonOffset);
-    if (showNationBorders() && !rivalLinks.empty()) drawSegments2D(rivalLinks, Color{150, 40, 60, 220}, 1.5f * scale, vr, lonOffset);
+    if (showNationBorders() && showDiplomacy && !rivalLinks.empty()) drawSegments2D(rivalLinks, Color{150, 40, 60, 220}, 1.5f * scale, vr, lonOffset);
     if (showTradeRoutes() && !tradeSea.empty())  drawSegments2D(tradeSea, Color{90, 200, 235, 220}, 1.2f * scale, vr, lonOffset);
     if (showTradeRoutes() && !tradeLand.empty()) drawSegments2D(tradeLand, Color{230, 180, 90, 220}, 1.2f * scale, vr, lonOffset);
     if (showDrift   && !driftArrows.empty()) drawSegments2D(driftArrows, Color{90, 230, 255, 255}, 2.0f * scale, vr, lonOffset);
@@ -464,6 +464,25 @@ void Viewer::drawMapOverlays(Rectangle vr, double lonOffset, float scale, float
             DrawText(txt, (int)(lp.x + 4 * scale), (int)(lp.y - 8 * scale), fs, RAYWHITE);
         }
     }
+    // Realm labels (with the territory view): name kingdoms/empires at their capital. Mirrors the
+    // 3D realm-label block in renderFrame() -- previously 2D-only had none, so neither the on-screen
+    // map nor exportMapImage() ever showed realm names, only the 3D globe did.
+    if (drawLabels && showNationBorders() && !planet.nationList().empty()) {
+        for (const Nation& nat : planet.nationList()) {
+            if (nat.tier == NationTier::CityState) continue;    // declutter: only multi-settlement realms
+            if (nat.capital < 0 || nat.capital >= (int)planet.settlements.size()) continue;
+            int cell = planet.settlements[nat.capital].cell;
+            if (cell < 0 || cell >= (int)planet.cells.size()) continue;
+            int font = (int)std::round((nat.tier == NationTier::Empire ? 16 : 14) * scale);
+            if (font <= 0) continue;
+            double lon, lat; dirToLonLat(planet.cells[cell].unit, lon, lat);
+            Vector2 lp = projLonLat(lon, lat, lonOffset, vr);
+            if (!CheckCollisionPointRec(lp, vr)) continue;
+            int w = MeasureText(nat.name.c_str(), font);
+            DrawText(nat.name.c_str(), (int)lp.x - w / 2 + 1, (int)lp.y - font - 7, font, Color{0, 0, 0, 205});
+            DrawText(nat.name.c_str(), (int)lp.x - w / 2,     (int)lp.y - font - 8, font, Color{245, 235, 210, 255});
+        }
+    }
     // Place-name labels (the atlas). Minor features only when the map is zoomed in (on-screen) or
     // always for a high-res export, where there's ample room for the full detail. Skipped entirely
     // when the caller (exportAtlasImage) does its own decluttered label pass instead.
@@ -582,6 +601,24 @@ void Viewer::exportAtlasImage() {
             labels.push_back({ lp, &f.name, (int)std::round(font * labelScale), col, prio, (float)f.size, dot });
         }
     }
+    // Realm names (kingdoms/empires), regardless of the current colour mode -- an atlas is a
+    // reference, not "what you're currently looking at". Offset above the capital's own marker/name
+    // (rather than sharing its exact anchor point) so the two don't fight over the same box in the
+    // decluttering pass below; city-states are skipped (bare settlement name already covers them).
+    if (!planet.nationList().empty()) {
+        for (const Nation& nat : planet.nationList()) {
+            if (nat.tier == NationTier::CityState || nat.name.empty()) continue;
+            if (nat.capital < 0 || nat.capital >= (int)planet.settlements.size()) continue;
+            int cell = planet.settlements[nat.capital].cell;
+            if (cell < 0 || cell >= (int)planet.cells.size()) continue;
+            int font = (int)std::round((nat.tier == NationTier::Empire ? 16 : 14) * labelScale);
+            int prio = nat.tier == NationTier::Empire ? 0 : 1;
+            double lon, lat; dirToLonLat(planet.cells[cell].unit, lon, lat);
+            Vector2 lp = projLonLat(lon, lat, mapLon, er);
+            lp.y -= font * 0.9f;
+            labels.push_back({ lp, &nat.name, font, Color{245, 235, 210, 255}, prio, (float)nat.totalPop, false });
+        }
+    }
     if (!planet.settlements.empty()) {
         const double townP = planet.cfg.civTownPop, cityP = planet.cfg.civCityPop, abP = planet.cfg.civAbandonPop;
         for (const Settlement& s : planet.settlements) {